1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * aes-ccm-glue.c - AES-CCM transform for ARMv8 with Crypto Extensions
4  *
5  * Copyright (C) 2013 - 2017 Linaro Ltd <ard.biesheuvel@linaro.org>
6  */
7 
8 #include <asm/neon.h>
9 #include <asm/simd.h>
10 #include <asm/unaligned.h>
11 #include <crypto/aes.h>
12 #include <crypto/scatterwalk.h>
13 #include <crypto/internal/aead.h>
14 #include <crypto/internal/simd.h>
15 #include <crypto/internal/skcipher.h>
16 #include <linux/module.h>
17 
18 #include "aes-ce-setkey.h"
19 
20 static int num_rounds(struct crypto_aes_ctx *ctx)
21 {
22 	/*
23 	 * # of rounds specified by AES:
24 	 * 128 bit key		10 rounds
25 	 * 192 bit key		12 rounds
26 	 * 256 bit key		14 rounds
27 	 * => n byte key	=> 6 + (n/4) rounds
28 	 */
29 	return 6 + ctx->key_length / 4;
30 }
31 
32 asmlinkage void ce_aes_ccm_auth_data(u8 mac[], u8 const in[], u32 abytes,
33 				     u32 *macp, u32 const rk[], u32 rounds);
34 
35 asmlinkage void ce_aes_ccm_encrypt(u8 out[], u8 const in[], u32 cbytes,
36 				   u32 const rk[], u32 rounds, u8 mac[],
37 				   u8 ctr[]);
38 
39 asmlinkage void ce_aes_ccm_decrypt(u8 out[], u8 const in[], u32 cbytes,
40 				   u32 const rk[], u32 rounds, u8 mac[],
41 				   u8 ctr[]);
42 
43 asmlinkage void ce_aes_ccm_final(u8 mac[], u8 const ctr[], u32 const rk[],
44 				 u32 rounds);
45 
46 static int ccm_setkey(struct crypto_aead *tfm, const u8 *in_key,
47 		      unsigned int key_len)
48 {
49 	struct crypto_aes_ctx *ctx = crypto_aead_ctx(tfm);
50 
51 	return ce_aes_expandkey(ctx, in_key, key_len);
52 }
53 
54 static int ccm_setauthsize(struct crypto_aead *tfm, unsigned int authsize)
55 {
56 	if ((authsize & 1) || authsize < 4)
57 		return -EINVAL;
58 	return 0;
59 }
60 
61 static int ccm_init_mac(struct aead_request *req, u8 maciv[], u32 msglen)
62 {
63 	struct crypto_aead *aead = crypto_aead_reqtfm(req);
64 	__be32 *n = (__be32 *)&maciv[AES_BLOCK_SIZE - 8];
65 	u32 l = req->iv[0] + 1;
66 
67 	/* verify that CCM dimension 'L' is set correctly in the IV */
68 	if (l < 2 || l > 8)
69 		return -EINVAL;
70 
71 	/* verify that msglen can in fact be represented in L bytes */
72 	if (l < 4 && msglen >> (8 * l))
73 		return -EOVERFLOW;
74 
75 	/*
76 	 * Even if the CCM spec allows L values of up to 8, the Linux cryptoapi
77 	 * uses a u32 type to represent msglen so the top 4 bytes are always 0.
78 	 */
79 	n[0] = 0;
80 	n[1] = cpu_to_be32(msglen);
81 
82 	memcpy(maciv, req->iv, AES_BLOCK_SIZE - l);
83 
84 	/*
85 	 * Meaning of byte 0 according to CCM spec (RFC 3610/NIST 800-38C)
86 	 * - bits 0..2	: max # of bytes required to represent msglen, minus 1
87 	 *                (already set by caller)
88 	 * - bits 3..5	: size of auth tag (1 => 4 bytes, 2 => 6 bytes, etc)
89 	 * - bit 6	: indicates presence of authenticate-only data
90 	 */
91 	maciv[0] |= (crypto_aead_authsize(aead) - 2) << 2;
92 	if (req->assoclen)
93 		maciv[0] |= 0x40;
94 
95 	memset(&req->iv[AES_BLOCK_SIZE - l], 0, l);
96 	return 0;
97 }
98 
99 static void ccm_update_mac(struct crypto_aes_ctx *key, u8 mac[], u8 const in[],
100 			   u32 abytes, u32 *macp)
101 {
102 	if (crypto_simd_usable()) {
103 		kernel_neon_begin();
104 		ce_aes_ccm_auth_data(mac, in, abytes, macp, key->key_enc,
105 				     num_rounds(key));
106 		kernel_neon_end();
107 	} else {
108 		if (*macp > 0 && *macp < AES_BLOCK_SIZE) {
109 			int added = min(abytes, AES_BLOCK_SIZE - *macp);
110 
111 			crypto_xor(&mac[*macp], in, added);
112 
113 			*macp += added;
114 			in += added;
115 			abytes -= added;
116 		}
117 
118 		while (abytes >= AES_BLOCK_SIZE) {
119 			aes_encrypt(key, mac, mac);
120 			crypto_xor(mac, in, AES_BLOCK_SIZE);
121 
122 			in += AES_BLOCK_SIZE;
123 			abytes -= AES_BLOCK_SIZE;
124 		}
125 
126 		if (abytes > 0) {
127 			aes_encrypt(key, mac, mac);
128 			crypto_xor(mac, in, abytes);
129 			*macp = abytes;
130 		}
131 	}
132 }
133 
134 static void ccm_calculate_auth_mac(struct aead_request *req, u8 mac[])
135 {
136 	struct crypto_aead *aead = crypto_aead_reqtfm(req);
137 	struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
138 	struct __packed { __be16 l; __be32 h; u16 len; } ltag;
139 	struct scatter_walk walk;
140 	u32 len = req->assoclen;
141 	u32 macp = 0;
142 
143 	/* prepend the AAD with a length tag */
144 	if (len < 0xff00) {
145 		ltag.l = cpu_to_be16(len);
146 		ltag.len = 2;
147 	} else  {
148 		ltag.l = cpu_to_be16(0xfffe);
149 		put_unaligned_be32(len, &ltag.h);
150 		ltag.len = 6;
151 	}
152 
153 	ccm_update_mac(ctx, mac, (u8 *)&ltag, ltag.len, &macp);
154 	scatterwalk_start(&walk, req->src);
155 
156 	do {
157 		u32 n = scatterwalk_clamp(&walk, len);
158 		u8 *p;
159 
160 		if (!n) {
161 			scatterwalk_start(&walk, sg_next(walk.sg));
162 			n = scatterwalk_clamp(&walk, len);
163 		}
164 		p = scatterwalk_map(&walk);
165 		ccm_update_mac(ctx, mac, p, n, &macp);
166 		len -= n;
167 
168 		scatterwalk_unmap(p);
169 		scatterwalk_advance(&walk, n);
170 		scatterwalk_done(&walk, 0, len);
171 	} while (len);
172 }
173 
174 static int ccm_crypt_fallback(struct skcipher_walk *walk, u8 mac[], u8 iv0[],
175 			      struct crypto_aes_ctx *ctx, bool enc)
176 {
177 	u8 buf[AES_BLOCK_SIZE];
178 	int err = 0;
179 
180 	while (walk->nbytes) {
181 		int blocks = walk->nbytes / AES_BLOCK_SIZE;
182 		u32 tail = walk->nbytes % AES_BLOCK_SIZE;
183 		u8 *dst = walk->dst.virt.addr;
184 		u8 *src = walk->src.virt.addr;
185 		u32 nbytes = walk->nbytes;
186 
187 		if (nbytes == walk->total && tail > 0) {
188 			blocks++;
189 			tail = 0;
190 		}
191 
192 		do {
193 			u32 bsize = AES_BLOCK_SIZE;
194 
195 			if (nbytes < AES_BLOCK_SIZE)
196 				bsize = nbytes;
197 
198 			crypto_inc(walk->iv, AES_BLOCK_SIZE);
199 			aes_encrypt(ctx, buf, walk->iv);
200 			aes_encrypt(ctx, mac, mac);
201 			if (enc)
202 				crypto_xor(mac, src, bsize);
203 			crypto_xor_cpy(dst, src, buf, bsize);
204 			if (!enc)
205 				crypto_xor(mac, dst, bsize);
206 			dst += bsize;
207 			src += bsize;
208 			nbytes -= bsize;
209 		} while (--blocks);
210 
211 		err = skcipher_walk_done(walk, tail);
212 	}
213 
214 	if (!err) {
215 		aes_encrypt(ctx, buf, iv0);
216 		aes_encrypt(ctx, mac, mac);
217 		crypto_xor(mac, buf, AES_BLOCK_SIZE);
218 	}
219 	return err;
220 }
221 
222 static int ccm_encrypt(struct aead_request *req)
223 {
224 	struct crypto_aead *aead = crypto_aead_reqtfm(req);
225 	struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
226 	struct skcipher_walk walk;
227 	u8 __aligned(8) mac[AES_BLOCK_SIZE];
228 	u8 buf[AES_BLOCK_SIZE];
229 	u32 len = req->cryptlen;
230 	int err;
231 
232 	err = ccm_init_mac(req, mac, len);
233 	if (err)
234 		return err;
235 
236 	if (req->assoclen)
237 		ccm_calculate_auth_mac(req, mac);
238 
239 	/* preserve the original iv for the final round */
240 	memcpy(buf, req->iv, AES_BLOCK_SIZE);
241 
242 	err = skcipher_walk_aead_encrypt(&walk, req, false);
243 
244 	if (crypto_simd_usable()) {
245 		while (walk.nbytes) {
246 			u32 tail = walk.nbytes % AES_BLOCK_SIZE;
247 
248 			if (walk.nbytes == walk.total)
249 				tail = 0;
250 
251 			kernel_neon_begin();
252 			ce_aes_ccm_encrypt(walk.dst.virt.addr,
253 					   walk.src.virt.addr,
254 					   walk.nbytes - tail, ctx->key_enc,
255 					   num_rounds(ctx), mac, walk.iv);
256 			kernel_neon_end();
257 
258 			err = skcipher_walk_done(&walk, tail);
259 		}
260 		if (!err) {
261 			kernel_neon_begin();
262 			ce_aes_ccm_final(mac, buf, ctx->key_enc,
263 					 num_rounds(ctx));
264 			kernel_neon_end();
265 		}
266 	} else {
267 		err = ccm_crypt_fallback(&walk, mac, buf, ctx, true);
268 	}
269 	if (err)
270 		return err;
271 
272 	/* copy authtag to end of dst */
273 	scatterwalk_map_and_copy(mac, req->dst, req->assoclen + req->cryptlen,
274 				 crypto_aead_authsize(aead), 1);
275 
276 	return 0;
277 }
278 
279 static int ccm_decrypt(struct aead_request *req)
280 {
281 	struct crypto_aead *aead = crypto_aead_reqtfm(req);
282 	struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
283 	unsigned int authsize = crypto_aead_authsize(aead);
284 	struct skcipher_walk walk;
285 	u8 __aligned(8) mac[AES_BLOCK_SIZE];
286 	u8 buf[AES_BLOCK_SIZE];
287 	u32 len = req->cryptlen - authsize;
288 	int err;
289 
290 	err = ccm_init_mac(req, mac, len);
291 	if (err)
292 		return err;
293 
294 	if (req->assoclen)
295 		ccm_calculate_auth_mac(req, mac);
296 
297 	/* preserve the original iv for the final round */
298 	memcpy(buf, req->iv, AES_BLOCK_SIZE);
299 
300 	err = skcipher_walk_aead_decrypt(&walk, req, false);
301 
302 	if (crypto_simd_usable()) {
303 		while (walk.nbytes) {
304 			u32 tail = walk.nbytes % AES_BLOCK_SIZE;
305 
306 			if (walk.nbytes == walk.total)
307 				tail = 0;
308 
309 			kernel_neon_begin();
310 			ce_aes_ccm_decrypt(walk.dst.virt.addr,
311 					   walk.src.virt.addr,
312 					   walk.nbytes - tail, ctx->key_enc,
313 					   num_rounds(ctx), mac, walk.iv);
314 			kernel_neon_end();
315 
316 			err = skcipher_walk_done(&walk, tail);
317 		}
318 		if (!err) {
319 			kernel_neon_begin();
320 			ce_aes_ccm_final(mac, buf, ctx->key_enc,
321 					 num_rounds(ctx));
322 			kernel_neon_end();
323 		}
324 	} else {
325 		err = ccm_crypt_fallback(&walk, mac, buf, ctx, false);
326 	}
327 
328 	if (err)
329 		return err;
330 
331 	/* compare calculated auth tag with the stored one */
332 	scatterwalk_map_and_copy(buf, req->src,
333 				 req->assoclen + req->cryptlen - authsize,
334 				 authsize, 0);
335 
336 	if (crypto_memneq(mac, buf, authsize))
337 		return -EBADMSG;
338 	return 0;
339 }
340 
341 static struct aead_alg ccm_aes_alg = {
342 	.base = {
343 		.cra_name		= "ccm(aes)",
344 		.cra_driver_name	= "ccm-aes-ce",
345 		.cra_priority		= 300,
346 		.cra_blocksize		= 1,
347 		.cra_ctxsize		= sizeof(struct crypto_aes_ctx),
348 		.cra_module		= THIS_MODULE,
349 	},
350 	.ivsize		= AES_BLOCK_SIZE,
351 	.chunksize	= AES_BLOCK_SIZE,
352 	.maxauthsize	= AES_BLOCK_SIZE,
353 	.setkey		= ccm_setkey,
354 	.setauthsize	= ccm_setauthsize,
355 	.encrypt	= ccm_encrypt,
356 	.decrypt	= ccm_decrypt,
357 };
358 
359 static int __init aes_mod_init(void)
360 {
361 	if (!cpu_have_named_feature(AES))
362 		return -ENODEV;
363 	return crypto_register_aead(&ccm_aes_alg);
364 }
365 
366 static void __exit aes_mod_exit(void)
367 {
368 	crypto_unregister_aead(&ccm_aes_alg);
369 }
370 
371 module_init(aes_mod_init);
372 module_exit(aes_mod_exit);
373 
374 MODULE_DESCRIPTION("Synchronous AES in CCM mode using ARMv8 Crypto Extensions");
375 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
376 MODULE_LICENSE("GPL v2");
377 MODULE_ALIAS_CRYPTO("ccm(aes)");
378